Electrophoretic Deposition of Ternary Metal Sulfide Electrochemical Electrodes with Tunable Pore Structure

Cornell University, Ithaca NY

Investigators

Abstract

This grant supports research that contributes new knowledge to the manufacturing of ternary metal sulfide electrochemical electrodes for energy storage applications. Complex metal sulfides are materials made from sulfur combined with more than one metal. These complex metal sulfides have emerged as a new and increasingly researched system for energy applications due to their high application performance, low cost, and portfolio of earth-abundant, non-toxic alternatives to standard materials. Compared to the currently used metal oxides, metal sulfides have demonstrated better electrical conductivity, greater mechanical and thermal stability, and higher performance. However, the widespread industrial integration of electrodes, which is the basis for most energy applications, made from metal sulfide nanostructures is impeded by the lack of large-scale production methods that are low cost, efficient, and simple. Additionally, one of the important but often overlooked design parameters for electrodes is the pore structure, which plays an important role in increasing performance. This grant addresses both issues by investigating methods for scalable nanomanufacturing of complex metal sulfide nanocrystals and assembling them into optimum porous electrode structures. The outcome of this grant benefits the U.S. economy and society because electrochemical electrodes are key components of batteries and supercapacitors, which power and store energy for many devices and applications in modern society. This work advances the next generation of electrochemical energy materials, leading to improvements in energy conversion, storage, and lowering of cost. It broadens the participation of underrepresented groups and promotes teaching and learning by developing lending library modules. Current injection methods for synthesis of ternary sulfide nanocrystals suffers from low conversion yield and poor reproducibility This project overcomes these technical barriers by manufacturing ternary sulfide nanocrystals through a solvent-less synthesis method, employing highly reactive anion precursors, such as ammonium sulfide, and metal carboxylates in the organic phase. This research uses electrophoretic deposition to assemble the complex metal sulfide nanocrystals into electrochemical electrodes with controlled porosity. The nanocrystal building-blocks are uniform in size and no additives are used, which permits tailoring and quantification of the packing and pore structure of the electrode. The research team seeks to achieve high-fidelity printing of thin three-dimensional electrode films with tunable pore size by directed assembly of colloidal particles in electric fields. The research investigates non-linear applied potentials and characterizes the films with methods including electrochemical impedance spectroscopy, Voronoi tessellations to quantify the pore structure, and radial distribution function analysis. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.